The present invention relates to a rotor blade for a first phase of a gas turbine.
Gas turbine refers to a rotating thermal machine which converts the enthalpy of a gas into useful energy, using gases coming from a combustion, and which supplies mechanical power on a rotating shaft.
The turbine therefore normally comprises a compressor or turbo-compressor, inside which the air taken from the outside environment is brought under pressure.
Various injectors feed the fuel which is mixed with the air to form an air-fuel ignition mixture.
The axial compressor is entrained by a turbine, in the true sense, i.e. a turbo-expander, which supplies mechanical energy to a user transforming the enthalpy of the gases combusted in the combustion chamber.
In applications for the generation of mechanical energy, the expansion jump is subdivided into two partial jumps, each of which takes place inside a turbine. The high-pressure turbine, downstream of the combustion chamber, entrains the compressor. The low-pressure turbine, which collects the gases coming from the high-pressure turbine, is then connected to a user.
The turbo-expander, turbo-compressor, combustion chamber (or heater), outlet shaft, regulation system and ignition system, form the essential parts of a gas turbine plant.
As far as the functioning of a gas turbine is concerned, it is known that the fluid penetrates the compressor through a series of inlet ducts.
In these canalizations, the gas has low-pressure and low-temperature characteristics, whereas, as it passes through the compressor, the gas is compressed and its temperature increases.
It then penetrates into the combustion (or heating) chamber, where it undergoes a further significant increase in temperature.
The heat necessary for the temperature increase of the gas is supplied by the combustion of liquid fuel introduced into the heating chamber, by means of injectors.
The triggering of the combustion, when the machine is activated, is obtained by means of sparking plugs.
At the outlet of the combustion chamber, the high-pressure and high-temperature gas reaches the turbine, through specific ducts, where it gives up part of the energy accumulated in the compressor and heating chamber (combustor) and then flows outside by means of the discharge channels.
As the energy conferred by the gas to the turbine is greater than that absorbed thereby in the compressor, a certain quantity of energy remains available, on the shaft of the machine, which purified of the work absorbed by the accessories and passive resistances of the moving mechanical organs, forms the useful work of the plant.
As a result of the high specific energy made available, the turbines in the true sense, i.e. the turbo-expanders, are generally multi-phase to optimize the yield of the energy transformation transferred by the gas into useful work.
The phase is therefore the constitutive element for each section of a turbine and comprises a stator and a rotor, each equipped with a series of blades.
One of the main requisites common to all turbines, however, is linked to the high efficiency which must be obtained for operating on all the components of the turbine.
In recent years, technologically avant-garde turbines have been further improved, by raising the thermodynamic cycle parameters such as combustion temperature, pressure changes, efficacy of the cooling system and components of the turbine.
Nowadays, for a further improvement in efficiency, it is necessary to operate on the aerodynamic parameters of the profiles of the blade system.
The geometrical configuration of the blade system significantly influences the aerodynamic efficiency.
This depends on the fact that the geometrical characteristics of the blade determine the distribution of the relative fluid rates, consequently influencing the distribution of the limit layers along the walls and, last but not least, friction losses.
In a low-pressure turbine, it is observed that the rotation rate operating conditions can vary from 50% to 105% of the nominal rate and consequently, the blade system of the turbines must maintain a high aerodynamic efficiency within a very wide range.
Particularly in the case of rotor blades of a first phase of a low-pressure turbine, an extremely high efficiency is required, at the same time maintaining an appropriate aerodynamic and mechanical load.
At present, it is difficult to have blades which allow a high efficiency with variations in the functioning conditions of the turbine and which, at the same time, are capable of maintaining a useful life.
An objective of the present invention is to provide a rotor blade for a first phase of a gas turbine which allows high aerodynamic performances within a wide functioning range.
A further objective is to provide a rotor blade for a first phase of a gas turbine which, at the same time, enables a high useful life of the component itself.
Another objective is to provide a rotor blade for a first phase of a gas turbine which allows high aerodynamic performances within a wide functioning range and which, at the same time, enables a useful life of the component itself.
Further characteristics of the invention are indicated in the specification and claims.
The characteristics and advantages of a rotor blade for a first phase of a gas turbine according to the present invention will appear more evident from the following, illustrative and non-limiting description, referring to the enclosed schematic drawings in which: